drm protected error on authorized sony e reader

My wife has a Sony PRS T2 reader but ‘borrowbox’ no longer allows downloads via reader for PC . So she downloaded the books to ADE and using file explorer, manually transferred the e pub file from ‘my digital editions’ to sony reader, media, books. Her ADE and reader for PC and the reader are all authorized with her adobe account but attempts to open the book give error DRM protected . I did this for my similar hardware a few months ago although ADE did not require authorization and books opened OK on the PRS T2 reader. Has ADE changed to prevent book opening? Any Ideas?